Strategies for the early detection of autism spectrum disorders (ASD) in people with intellectual developmental disorder (IDD) are urgently needed, but few specific tools have been developed. The present study examines the psychometric properties of the EVTEA-DI, a Spanish adaptation of the PDD-MRS, in a large randomized sample of 979 adults with IDD. Factorial solution analysis suggested a three-factor solution (stereotyped behavior, communication, and social behavior). The EVTEA-DI showed good reliability and convergent validity when compared to the Childhood Autism Rating Scale. Discriminative validity analysis resulted in an acceptable global sensitivity of 70% and a high specificity of 90%. The EVTEA-DI proved to be a valid screening tool in ASD assessment of the adult Spanish population with IDD.